Cata Levling

I am going to begin to level my priest alt now from 80-85 and i was wondering if someone could help me with a good lvl 80 specc that i can use while i do start to lvl.
I am going to do dungeons with a mate of mine as a tank so.

For solo questing, you'll go well as Shadow. Prolly want something like this to set yourself up for end game DPS.

For dungeons, it depends if you're gonna be healing or DPS. Overall, you're gonna be fine whether you choose to do Disc or Holy as a healer in pre-heroic 5-mans. However, I think the rage-based tanks prefer not to have as many absorbs in play... Can't remember. Also, the Disc absorbs may affect the Cata tank effect (Vengeance), which may annoy your mate.

Recently did this, the builds onorvele mentioned are pretty much it, there isn't that much room to do anything else.

Pretty much you take shadow/holy as your two specs. Solo using shadow and when you just quest with friend (you won't need dedicated heals, just drop shadow form for a quick heal), use holy for dungeons so you get groups faster If you've never healed before, I wouldn't worry about it, it is very easy pre-heriocs, there is room for error and the gear is virtually the same between your shadow/holy 80-85.

All the content other than the Ring of X type things I found to be soloable as a shadow priest, I mean really as long as the mob deals less dmg to you than you can heal, you can take down anything over time, thanks to Machoism which gives you near infinite mana.

For solo questing, you'll go well as Shadow. Prolly want something like this to set yourself up for end game DPS.

For dungeons, it depends if you're gonna be healing or DPS. Overall, you're gonna be fine whether you choose to do Disc or Holy as a healer in pre-heroic 5-mans. However, I think the rage-based tanks prefer not to have as many absorbs in play... Can't remember. Also, the Disc absorbs may affect the Cata tank effect (Vengeance), which may annoy your mate.

The Shield - Rage issue was solved quite a while ago. I don't know about Vengeance but I've never heard that being a problem.
To the OP: For questing I would highly advice you to go Shadow. In dungeons you can either stay Shadow and DPS, or Heal as either Holy or Discipline. Both specs should serve you well.